Faulty pneumatic actuator on 8110's grappler claws?

[Out of Sight]

Guys, I had recently finished building my 8110 Unimog. I have a problem with the smaller pneumatic actuator (4625540) which opens/closes the grapple claw. The problem is each time I flick the switch to close it FULLY (both claws touching each other in closed position with actuator fully extended), it won't open again unless I build up some good pressure on the air lines, flick the switch quickly to send all the pressure. I'd checked for blocked air hoses or leaky ones,binding pivot joins on the grapple claws, and even swapped the switch to make sure that the switch isn't faulty. Everything is fine.

I inspected the actuator itself, i noticed that when fully extended, it's notably stiff to retract back as if the seals are binding inside(air hoses detached to avoid pressure build up inside the cylinder), . However when not fully extended the actuator performs well. It only binds towards the extension's end point. I checked also for bent shafts, nope everything looks fine. I tried adding some 100% silicone oil on the shaft, to no avail.

I'm thinking of contacting Lego CS for a replacment part, but before that I need to be sure,do I have a faulty actuator?

Thanks guys

[Alasdair Ryan]

I would say the cause of your problem is the mini pneumatic ram too.Did you check both the inlet and the outlet to the ram?

Edited September 5, 2012 by Alasdair Ryan

[allanp]

I would also aree that it's a problem charachteristic of the ram. I have a few of these rams and they all seem to be a little stiff to begin with. Over time they do wear in nicely tho. It still may be that the seal is just slightly too big and is binding tho. Do you have any other small cylinders to compare them?

[dr_spock]

I find the mini one on mine seems to need more air pressure to operate than the larger cylinders. Adding an air tank seems to help it work faster.

[Out of Sight]

Thanks guys for your response.

Yes I checked the inlet and outlet...but I'm only seeing through tiny holes ..should there be anything I must be aware of? Visually there doesn't seem to be anything blocking though. This is actually my first time owning a pneumatic set, so I haven't got any other mini pneumatic cylinder to compare it to.

But I did request a replacement part from Lego. If it turns out that I have a faulty cylinder, than I can only hope that the new one is smoother.

[captainmib]

maybe it's the distance towards the actuator? The small one is quite far from the pump.

But i noticed this aswell.

[Out of Sight]

maybe it's the distance towards the actuator? The small one is quite far from the pump.

But i noticed this aswell.

Aha..so I'm not alone here But as been said, it's probably the characteristic of the ram. Yeah the distance from the switch could also be the cause as well. I'm currently taking of the mini actuator and cycling it back and forth slowly with my hands just to see if i can 'loosen' it up a little.

[skylinedan]

The rubber ends get stuck together on the grapple, if you eliminate them it will open and close just fine. I had this issue with both of mine,and took the rubber ends off fixing it.

Dan

[z3_2drive]

yeah I had similar thing with mine, I think its just the distance the air needs to travel